 For our first set of practice problems, we're given a graph and we're asked to find the coordinates of the center and the radius and with that information we're going to write an equation of the circle. So these are quite simple if you know how to plug the equation into our standard equation of a circle and we'll start by just finding this point on our graph. Now at the center of our circle, we're just going to find the x value negative 1 and we're going to count up positive 4 is going to be our center and next we're asked to find the radius and for the radius, if we're given a graph, all we have to do is count from the center either horizontally out or up and down vertically to the edge of the circle and in all cases that's going to be a measure of 3. And now we can write the equation of our circle by following the standard equation of a circle. Remember our x and y value is going to be the opposite sign of what the center values are for that coordinate. So my x coordinate is negative 1, I'll change that to positive 1 in my equation and at the same time my y coordinate is positive 4, I'll change that to a negative 4 and I set that equal to the radius and we have to square the radius and so the last step I'm going to leave the x and y values like that, 3 squared is 9 and this is the equation of this circle. Just a quick double check at the end, my x value is negative so in my equation it's positive, y value positive in the equation it's negative and then I take the radius squared. We'll do the same thing for the next problem, we're going to identify the coordinate of the center and then count out the radius of the circle and we'll just plug that into our equation. So my center of the circle if I counted out x value negative 1 and then I'm going down 3, so the center of my circle negative 1, negative 3, the radius of the circle if I start out at the center and then I can count out either left, right, up or down in all directions I'm going to count out a value of 4 for my radius and so when I plug that back into the standard equation of a circle I'm going to have x because this is a negative one I'm going to make that a positive 1 squared and then y, the negative 3 becomes positive 3 squared equals my radius squared and the last step is to just simplify that radius, 4 squared is 16.